Mixins

All mixins live in pragmatic.mixins.

Form Mixins

ReadOnlyFormMixin

Makes specific form fields read-only and disabled on existing instances.

from pragmatic.mixins import ReadOnlyFormMixin
from django import forms

class ProfileForm(ReadOnlyFormMixin, forms.ModelForm):
    read_only = ('username', 'email')

    class Meta:
        model = User
        fields = ['username', 'email', 'first_name']

Fields listed in read_only have readonly and disabled attributes added to their widgets and are excluded from validation (they return the current instance value through a custom clean_<field> method).

Set read_only_without_instance = True to enforce read-only even when there is no instance.pk (useful for display-only forms that never have an instance).

PickadayFormMixin

Fixes pickaday.js date/datetime inputs by adding a data-value attribute in the format specified by settings.DATE_FORMAT.

from pragmatic.mixins import PickadayFormMixin

class EventForm(PickadayFormMixin, forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.fix_fields(self, *args, **kwargs)

Access Control Mixins

LoginPermissionRequiredMixin

Extends Django’s PermissionRequiredMixin with raise_exception = True and stores the missing permission on request.user.permission_error for use in error handlers.

from pragmatic.mixins import LoginPermissionRequiredMixin

class InvoiceListView(LoginPermissionRequiredMixin, ListView):
    permission_required = 'billing.view_invoice'

StaffRequiredMixin

Restricts a view to staff users (is_staff or is_superuser). Unauthenticated or non-staff requests are redirected to settings.LOGIN_REDIRECT_URL with a flash error message.

from pragmatic.mixins import StaffRequiredMixin

class AdminDashboard(StaffRequiredMixin, TemplateView):
    template_name = 'admin/dashboard.html'

Set raise_exception = True on the class to raise PermissionDenied instead of redirecting.

SuperuserRequiredMixin

Same as StaffRequiredMixin but restricts to superusers only.

Delete Mixins

DeleteObjectMixin

Handles object deletion in a DeleteView. Override get_success_url() and optionally get_back_url() / get_failure_url().

from pragmatic.mixins import DeleteObjectMixin
from django.views.generic import DeleteView

class ArticleDeleteView(DeleteObjectMixin, DeleteView):
    model = Article
    success_url = reverse_lazy('article-list')

When PRAGMATIC_TRACK_DELETED_OBJECTS = True, a DeletedObject record is created on successful deletion.

On ProtectedError (related objects block deletion), the view redirects to get_failure_url() with a flash error.

Customisable attributes:

title — page title (default: 'Delete object')
message_success — flash message on success
message_error — flash message on ProtectedError
back_url — URL to return to; falls back to object.get_absolute_url()
failure_url — URL on failure; falls back to back_url

CheckProtectedDeleteObjectMixin

Extends DeleteObjectMixin. Before showing the confirmation page, it inspects NestedObjects and, if any protected relations exist, redirects immediately with an error listing the blocking object types and counts.

from pragmatic.mixins import CheckProtectedDeleteObjectMixin

class CustomerDeleteView(CheckProtectedDeleteObjectMixin, DeleteView):
    model = Customer
    success_url = reverse_lazy('customer-list')

List View Mixins

SafePaginator

A Paginator subclass that clamps out-of-range page numbers to the last page rather than raising EmptyPage. Also supports an optional count_only_id=True argument to count using .only('id') for performance.

from pragmatic.mixins import SafePaginator

class ArticleListView(ListView):
    paginator_class = SafePaginator

DisplayListViewMixin

Supports multiple display modes (e.g. list, table, map) controlled by a ?display= query parameter. Automatically sets template_name_suffix to _{display}, so a table display resolves to myapp/article_table.html.

from pragmatic.mixins import DisplayListViewMixin

class ArticleListView(DisplayListViewMixin, ListView):
    model = Article
    displays = ['list', 'table']
    paginate_by_display = {
        'list': [10, 25, 50],
        'table': 100,
    }

The active display defaults to the first entry in displays. Per-display pagination values are read from paginate_by_display; the first value in the list is the default.

Context variables added: display_modes, paginate_by_display, paginate_by.

SortingListViewMixin

URL-parameter-driven queryset sorting via ?sorting=<key>.

from pragmatic.mixins import SortingListViewMixin

class ArticleListView(SortingListViewMixin, ListView):
    model = Article
    sorting_options = {
        '-created': 'Newest first',
        'title': 'Title A–Z',
        # tuple form: (display_label, queryset_ordering)
        '-price': ('Price high–low', '-price'),
    }

The active sorting defaults to the first key. Negative prefixes (-field) use F(field).desc(nulls_last=True).

Context variable added: sorting_options.

PaginateListViewMixin

Minimal mixin that passes paginate_by from the view to the context. Use this when you need get_paginate_by() override without the full DisplayListViewMixin.

Model Mixins

SlugMixin

Auto-generates a URL-safe slug on save(), ensuring uniqueness by appending an integer suffix if needed.

from pragmatic.mixins import SlugMixin
from django.db import models

class Article(SlugMixin, models.Model):
    title = models.CharField(max_length=200)
    slug = models.SlugField(unique=True)

    # Optional overrides:
    # SLUG_FIELD = 'title'        # source field (default)
    # MAX_SLUG_LENGTH = 150       # truncate before uniqueness check
    # FORCE_SLUG_REGENERATION = True  # regenerate on every save (default)

PDF Mixins

FPDFMixin

Helper for generating PDF responses using the fpdf2 library. Override write_pdf_content() to add content to self.pdf.

from pragmatic.mixins import FPDFMixin
from django.views.generic import View

class InvoicePdfView(FPDFMixin, View):
    orientation = FPDFMixin.ORIENTATION_PORTRAIT

    def get_filename(self):
        return 'invoice.pdf'

    def write_pdf_content(self):
        self.pdf.set_font('Arial', size=12)
        self.pdf.cell(200, 10, txt='Hello', ln=True)

    def get(self, request, *args, **kwargs):
        return self.render()

FPDFMixin constants:

FORMAT_A4 / ORIENTATION_PORTRAIT / ORIENTATION_LANDSCAPE
margin_left, margin_right, margin_top, margin_bottom (default 8 mm each)

PdfDetailMixin

Renders an existing DetailView template as a PDF by POSTing the rendered HTML to an external conversion API (HTMLTOPDF_API_URL or PRINTMYWEB_URL).

from pragmatic.mixins import PdfDetailMixin

class InvoicePdfView(PdfDetailMixin, DetailView):
    model = Invoice
    template_name = 'billing/invoice_pdf.html'
    inline = True  # True = inline in browser, False = download

    def get_filename(self):
        return f'invoice-{self.get_object().number}.pdf'

Set HTMLTOPDF_API_URL or PRINTMYWEB_URL (plus PRINTMYWEB_TOKEN) in your settings.